Cari Nierenberg, Reviewed By Kathleen M. Zelman (1-3-2011), "Leafy Greens -- Ranked and Rated"، WebMD, Retrieved 25-6-2016. Edited.
↑ United States Department of Agriculture, "National Nutrient Database for Standard Reference Release 28: Lettuce, cos or romaine, raw"، The National Agricultural Library, Retrieved 25-6-2016.